Steps to remediate the issue for two source objects containing the same value used to match with the target object.
Correct the issue with duplicate values in the source environment
in Directory Sync dashboard UI, edit the profile
Disable object relinking if it's enabled (For DSP AD to AD only).
Run Reset Profile
Validate the source object correctly matched to the correct target object
Edit profile and enable the object relinking if this was enabled prior to the remediation.(For DSP AD to AD only)
If this does not work, you may need to clear the target object before running the Reset Profile, and Sync steps. The sync did not update because some of the attributes are not looked at by the code after being initially created in the target. Removing the target object will allow for a new object to be created with the correct attribute value.
For Domino solution
Edit and save Domino record.
Reset sync profile
Clear all attributes set by Dirsync.
Contact Product Support if you have any questions or issues with the above.